Piston-rod scraping ring accommodated in a groove in a dashpot cap, and method of inserting such a ring in such a groove

ABSTRACT

A piston-rod scraping ring ( 7 ) of elastic material accommodated in an inward opening groove ( 9 ) in a dashpot cap ( 2 ) and especially intended to scrape water and dirt off a piston rod ( 1 ). The object is to allow the ring to be easily inserted into the groove and secured there until the overall dashpot is assembled. The groove is accordingly higher at its outer circumference and its inner circumference ( 12 ) is deformed, compressing the rim ( 8 ) in place.

DESCRIPTION

[0001] The present invention concerns, first, a piston-rod scraping ringaccommodated in a groove in a dashpot cap as recited in the preamble toclaim 1, and, second, a method of inserting such a ring in such agroove.

[0002] Piston-rod scraping rings of elastic materials, especiallyintended for scraping water and dirt off piston rods, and accommodatedin a groove in a dashpot cap are known from German 3 443 370 C2.

[0003] There are many many ways of securing such piston-rod scrapingrings to the upper cap of a dashpot. One way is disclosed in German 3443 370 C2. The cap is secured by means of a groove that is openradially and, in one direction, axially, by a sleeve that axially andradially encloses the rim around the ring and is forced into a bore inthe groove. The compression secures the sleeve and hence the ring. Thereis a drawback to this approach in that the sleeve necessitatesadditional material and work.

[0004] Another approach to attaching such a cap to a dashpot is knownfrom German Patent 1 140 705. The piston-rod scraping ring is againinserted in a groove that is open radially and, in one direction,axially, and secured there radially by compression at the end of theouter cylinder. One drawback to this approach is that the ring remainsloose and can accordingly get lost before it is finally secured inplace. Furthermore, to protect it from deformation or eccentricity, thecap must be inserted very precisely in the groove before the dashpot isassembled.

[0005] German 19 921 696 A1 discloses a seal accommodated in aninward-opening groove in a cap. The actual sealing mass employed in suchseals must be well inserted axially in the groove. Furthermore, the massmust be secured in the nut somehow or radially tensioned, making thegroove difficult to machine precisely and necessitating an additionalcomponent.

[0006] The object of the present invention is accordingly a piston-rodscraping ring and a groove in a dashpot cap improved to the extent thatthe ring can easily be inserted into the groove and secured there untilthe overall dashpot is assembled.

[0007] This object is attained in accordance with the present inventionas recited in the body of claim 1. Claims 2 through 4 address methods ofinserting a piston rod scraping ring in a groove in a dashpot cap.

[0008] The advantages of the present invention are that the ring can befastened to the cap by simple means and with low expenditure and beforethe dashpot is finally assembled. Embodiments of the present inventionwill now be specified with reference to the accompanying drawing,wherein

[0009]FIG. 1 is a transverse section through the dashpot cap and itsassociated components,

[0010]FIG. 2 is a larger-scale depiction, representing the situationbefore the ring has been secured, of the groove that accommodates thering,

[0011]FIG. 3 is an illustration similar to FIG. 2 representing thesituation after the ring has been inserted,

[0012]FIG. 4 depicts an alternative embodiment in the situationillustrated in FIG. 2, and

[0013]FIG. 5 depicts the same embodiment in the situation illustrated inFIG. 3.

[0014] Piston rods usually extend out of dashpots through caps thatclose off the dashpots' open ends. FIG. 1 shows such a piston rod 1 anddashpot cap 2. At its outer circumference 2, the cap is sealed offagainst an unillustrated outer dashpot cylinder by an O ring 3. Suchcaps can be fastened to the cylinders in various ways.

[0015] Cap 2 is provided with various components that center and sealrod 1 as it travels into and out of the cylinder. These components arepositioned in the vicinity of a bore that extends through cap 2.Positioned at the bottom of cap 2 is a low-friction bushing 4 thatcenters rod 1. Above bushing 4, a gasket 5 is accommodated in aninward-opening groove and provided with the requisite radial tension bya compression ring 6.

[0016] At the top of cap 2 is a ring 7 that scrapes water and dirt offthe section of piston rod 1 outside the cylinder as the rod enters it.

[0017] The rim 8 around piston-rod scraping ring 7 is accommodated in aninward opening groove 9 in dashpot cap 2. Prior to assembly of thedashpot, rim 8 is more or less uniformly high. Furthermore, as will beevident from FIG. 2, the height 10 of groove 9 is also more or lessuniform.

[0018] The height of the rim 8 around piston-rod scraping ring 7, whichis not illustrated in FIG. 2, approximately equals the height 10 ofgroove 9. Once piston-rod scraping ring 7 has been positioned with itsrim 8 in groove 9, the groove's outer wall 11 is forced against itsinner circumference 12 by a separate tool, a press for instance,compressing height 10 in the vicinity of the inner circumference.

[0019] A similar deformation is induced in the embodiment illustrated inFIGS. 4 and 5.

[0020] When the conditions wherein piston-rod scraping ring 7 will beemployed prescribe that it be forced even more firmly into groove 9,both the groove and the rim 8 around the ring can in their originalshape be higher toward the center. When outer wall 11 is deformed suchthat the height 10 of groove 9 decreases as it approaches innercircumference 12, the rim 8 around the ring will accordingly be morepowerfully compressed.

[0021] It is also possible for the height of the rim 8 around piston-rodscraping ring 7 to increase outwards, in which event its maximal heightwill approximately equal the height 10 of groove 9. The seating ofpiston-rod scraping ring 7 will then be secured, once outer wall 11 hasbeen deformed, by the interlocking structures and by additional axialcompression.

List of Parts

[0022] 1. piston rod 2. dashpot cap 3. O ring 4. bushing 5. gasket 6.compression ring 7. piston-rod scraping ring 8. rim 9. groove 10. heightof groove 11. wall 12. inner circumference of groove

1. Piston-rod scraping ring (7) of elastic material accommodated in aninward opening groove (9) in a dashpot cap (2) and especially intendedto scrape water and dirt off a piston rod (1), characterized in that thegroove is higher in the vicinity of its outer circumference and the rim(8) around the ring is axially compressed in the vicinity of the innercircumference (12) of the groove.
 2. Method of inserting the piston-rodscraping ring (7) into the groove (9) in a dashpot cap (2) recited inclaim 1, characterized in that the rim (8), which is intended to occupythe groove (9), has a height that is more or less uniform and isinserted into the groove, which has the same height (10) as the rim,subsequent to which at least the wall (11) of the groove at its innercircumference (12) is deformed, decreasing the height of the groove inthat vicinity.
 3. Method of inserting the piston-rod scraping ring (7)into the groove (9) in a dashpot cap (2) recited in claim 1,characterized in that the rim (8), which is intended to occupy thegroove (9), has a height [that is more or less non uniform] and isinserted into the groove, which has a height (10) that decreases as itapproaches the center, subsequent to which at least the wall (11) of thegroove at its inner circumference (12) is deformed, decreasing theheight of the groove in that vicinity
 4. Method of inserting thepiston-rod scraping ring (7) into the groove (9) in a dashpot cap (2)recited in claim 1, characterized in that the rim (8), which is intendedto occupy the groove (9), has a height that decreases as it approachesthe center and is inserted into the groove, which has a uniform height(10), subsequent to which at least the wall (11) of the groove at itsinner circumference (12) is deformed, decreasing the height of thegroove as it approaches the center and in that the original maximalheight of the rim (8) around the ring (7) approximately equals theoriginal height of the groove.